The drawing room in the big house was full of the sort of silence that is made by eight or nine good-quality brains working hard and separately, absolutely not a library silence, more like being in a vast digestive system. Small, fierce Naomi sat typing at her desk that looked out over the unsmooth Highland lawn, a hedge of Rugosa roses, the path to the sea, Carradale Point itself and the sea beyond. She wrote well over ninety books. The light in the room was low and seemed to be green. There was a sizeable mobile made of metal fish that very probably interpreted Darwinian theory.

In the plain, loaded shelves was a tan first edition inscribed to Nou by its author of The Seven Pillars of Wisdom, on top of which I had one Easter found a chocolate egg hidden. This was a rare success for me since the annual egg-hunt clues had as a rule a scientific and mathematical bias, with a strong seam of Scottish history. After Nou’s death, this volume went up to auction and I saw it again in a newspaper; what it was and what it meant to me so separate.

Nou was, in addition to being an Argyllshire councillor, though devoid of any whiff of landlordism or lairdliness, Mother of the Bakgatla tribe in Botswana, and frequently one or more of her honorary Bakgatla children would be staying at the big house.

Nobody said, but Nou, as well as coming from the intellectual purple, was also, though it infuriated her to be addressed thus, Lady Mitchison. Her late husband had been made a Labour life peer. I mention this at all only to introduce the ticklish subject of what to call the people who worked for her, since she was at once so clearly the product of at least two kinds of aristocracy and a good old-fashioned Red.

One evening we older children were asked by Percy, who did the gardening, although one did not call him the gardener, to gather caterpillars from the kitchen garden. The cabbage white has a caterpillar that is fat and striped like a wedding cravat; when you pick it up it looks interested at both ends. We took our catch, if you can call anything as docile as a few bowls of caterpillars a catch, in to Nellie, who certainly was not the cook.

The caterpillars, dipped in flour and nicely fried, appeared as the first course that night in deference to the palates of Nou’s guests from Botswana.

The dining table was enormous, thick, not polished but raw wood, aged, stained, practical; it was a rectangle with curved ends; there must be a geometrical term for this figure but I lack it. I do not mean an ellipse. There seemed in that atmosphere of intellectual certainty so little that was elliptical in the way my father was in person and in the way his mind worked. I am ashamed to say that I escaped from his intelligent failures of certainty to the Mitchisons’ apparent categoricalness with the cowardice that goes with a callow mind aspin. My father’s way offered no shelter, while that of the Mitchisons offered much of it and, or so it seemed, to spare. I was, as I am not now, sick for certainties. I now find them infertile and too often rooted in prejudice.

I wonder now whether I was ever actually invited at all to Carradale or whether I just hid within one family or another’s capacious kindness: Rowy was kind all through my youth in a sort of improvement on her late friend, my mother’s, way. An improvement, I mean, in that Rowy was alive. Nou’s daughter-in-law Lorna, married to Av (Nicholas Avrion in full, meaning the Victory of the People), came from Skye and always seemed to be carrying a baby in her arms. She never raised her voice and had the balanced selflessness that comes to only very few mothers. She was impossible to lie to. It was Ruth, Naomi’s oldest daughter-in-law, whom I loved and to whom I clung like stickyweed for years, though she never complained about it, even when I started sticking to her in the South as well. She was not a physically large person, nor did she shout. She seemed to see a great deal and to interpret it correctly but in silence. She was a doctor, musical, wore slim brown or grey shirts and sat at a tangent to the table. She was tangential in manner yet direct in thought; a mode I find increasingly appealing the longer I live. I wish she were alive now; hers was a singular note amid so much information and embodied, biological almost, confidence.

At the far end of the dining room was a sizeable brown painting, thickly impastoed. It was known as ‘The Goat in the Custard’, and worked surprisingly well as a splashback for the kippers that were left for each individual to fry for him or herself at breakfast, in a then remarkable item of culinary equipment, an electric frying pan. It is a miracle that the house smelt not of frying red herrings but of heather, wood, pipe smoke and wool. Heather smells like dust and honey both. Intellectuals smoked pipes then.

Sometimes, a piper would come up from Lochgilphead, and, perhaps, a squeezebox player, and we would dance in the library, which was called the ping-pong room. Nou, short, dense, wore garments of fantastic tribal splendour and simultaneous rationality, sandals, bright yet serious skirts and perhaps a serape or sash in acknowledgement of one or another of her encyclopaedic interests and convictions. She was unbending, solid, frowning; she looked like strength itself, like an animal, an armadillo or a Galapagos tortoise; absolutely not a pangolin. The pangolin looks as though his armour has only recently been donned. Nou was born in hers. She danced in a stately manner that attested to her sublime physical confidence. She was an advocate of the benefits of free love. I feared to be addressed by her, yet longed to get a smile from her. I felt easier in her house when she was not in the room and that this is not a particularly healthy state of mind. I do not think that she cared much for my mother or me; even as lame ducks, a class for which Nou had time, we were not interestingly lamed. I can imagine my mother getting Carradale all wrong, talking in the drawing room during the daytime or gossiping or noticing clothes or foods or smells. Certainly she would be overdressed. We were there together only one time, when I was two, so I cannot speak for her outfit during that summer of 1957.

Mealtime conversation was on the whole abstract or theoretical, whatever age you were. There was little people-talk unless it be of use, attached to a paper written, a law made, a proof offered. Avrion had made butter with Lorna’s breast milk, I seem to remember, and there was talk of self-made blood-pudding.

Two years ago, wandering around the Scottish National Portrait Gallery, I came face to face with Nou. There she was, miraculously at about my height, as never in life, dressed in blue, frowning, chin on hand, looking me straight in the eye. It was her portrait by Wyndham Lewis, which had been on the ping-pong room wall and under whose gaze, dancing this time to records of Scottish dance tunes, I fell in love for the first time with a grown human not resident in the ancient world. It is a love that came to nothing in the conventional sense so that it remains, for me at least, complete. Nor is it untried. The one who generated it absolutely without intent remains today a beloved friend and provided for years as it were an internal moral thermostat that I fell short of, but knew when I was doing so. It is not coincidental to my life as a novelist that he was a child in India and is a musical scientist. Nor is it coincidental to my private life.

Wyndham Lewis was a good choice to paint the young Nou. He got that density, that energy, that intellectual force. In the corner of the painting to the sitter’s right is a curious pair of antagonistic marks, written in paint, like scallops inverted, or fists opposed, conjunct yet fierce. If they encrypt Nou’s character, they do it well. The other attribute caught is her uncompromising seriousness, combined with an irresistibility, like that of some metal.